[Bug libc/21336] __libc_res_nsearch() leak?

["rob.krakora at bluepillar dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=21336

--- Comment #10 from Rob Krakora <rob.krakora at bluepillar dot com> ---
The leak is occurring in the eglibc 2.19 code below...however, in the glibc
2.25 code further below there is some code added to indicated to the layers
above that a malloc has occurred which would negate the my proposed patch. 
eglibc 2.19 and glibc 2.19 are closer and glibc 2.19 does not have the code to
indicate to the layers above that a malloc has occurred so it could possibly
have a leak???

eglibc 2.19:

                if (*thisanssizp < MAXPACKET
                    /* If the current buffer is not the the static
                       user-supplied buffer then we can reallocate
                       it.  */
                    && (thisansp != NULL && thisansp != ansp)
#ifdef FIONREAD
                    /* Is the size too small?  */
                    && (ioctl (pfd[0].fd, FIONREAD, thisresplenp) < 0
                        || *thisanssizp < *thisresplenp)
#endif
                    ) {
                        /* Always allocate MAXPACKET, callers expect
                           this specific size.  */
                        u_char *newp = malloc (MAXPACKET);
                        if (newp != NULL) {
                                *thisanssizp = MAXPACKET;
                                *thisansp = newp;
                        }
                }

glibc 2.25:

                if (*thisanssizp < MAXPACKET
                    /* If the current buffer is not the the static
                       user-supplied buffer then we can reallocate
                       it.  */
                    && (thisansp != NULL && thisansp != ansp)
#ifdef FIONREAD
                    /* Is the size too small?  */
                    && (ioctl (pfd[0].fd, FIONREAD, thisresplenp) < 0
                        || *thisanssizp < *thisresplenp)
#endif
                    ) {
                        /* Always allocate MAXPACKET, callers expect
                           this specific size.  */
                        u_char *newp = malloc (MAXPACKET);
                        if (newp != NULL) {
                                *thisanssizp = MAXPACKET;
                                *thisansp = newp;
                                if (thisansp == ansp2)
                                  *ansp2_malloced = 1;
                        }
                }

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